Document Detail

Influence of upper respiratory tract on liquid flow to and from fetal lungs.
MedLine Citation:
PMID:  3733629     Owner:  NLM     Status:  MEDLINE    
The experiments were designed to determine the influence of the upper respiratory tract (URT) on liquid flow in the fetal trachea. This flow probably influences pulmonary distension, which is thought to be a major determinant of prenatal lung development. In six fetal sheep the URT could be bypassed by connecting the lower trachea, via an external flowmeter, to a cannula in the amniotic sac. In confirmation of our earlier findings, when the URT was in circuit, the mean rate of tracheal efflux was greater during episodes of fetal breathing movements (FBM) [mean 13.8 +/- 2.6 (SE) ml/h] than during apneic periods (mean 3.2 +/- 1.0 ml/h). When the URT was bypassed there was a reversal of net tracheal flow during FBM episodes (mean 19.6 +/- 5.6 ml/h toward the lungs); during apnea there was a much greater rate of efflux (mean 33.1 +/- 10.2 ml/h) than when the URT was in circuit. Nonlabor uterine contractions were associated with an increased rate of efflux during apnea only when the URT was bypassed. We conclude that during fetal life the URT imposes an essentially unidirectional flow of pulmonary liquid away from the lungs, preventing ingress of amniotic fluid and maintaining constancy of composition of liquid in the developing airways. By retarding outward flow during periods of apnea and thoracic compression and by preventing net influx during episodes of FBM, the URT has the probable effect of maintaining the volume and composition of liquid in the fetal airways within narrow limits.
R Harding; A D Bocking; J N Sigger
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  61     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1986 Jul 
Date Detail:
Created Date:  1986-09-17     Completed Date:  1986-09-17     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  68-74     Citation Subset:  IM    
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MeSH Terms
Fetus / metabolism,  physiology*
Physiology / instrumentation
Respiratory Physiological Phenomena*
Respiratory System / embryology
Sheep / embryology
Trachea / embryology,  metabolism*
Uterine Contraction

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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